Ok since many a people here were posting some reviews on devices I thought I should post one of my own. I will not get indepth and discuss things which have been covered before many times. Ill actually try to keep this oriented towards the Indian scenerio about BlackBerries. Even if 1 person here finds this usefull ill consider the post worthwhile. Its kind-of giving back for all the information and help I've recieved through the forums here.
Very low buget (trying the waters)
Used/New 8700g & Used 81xx Pearl Series (Also consider 71xx and 72xx)
I would not reccomend any of these phones if you want to get any real work done actually. Because all of them are very outdated now-a-days and wont be very usefull. But are great phones to keep as standby considering the amount for which you can buy them for now-a-days (Rs 1000 ~ 3500 or max 5000 for a Pearl) bearing the pearl none of them have the trackball. And I have used the 8700g and find it a excellent phone for its battery backup and rough usage and the amazing cheap price. You can keep this as a second phone. I personally use one inside a otterbox mounted on my Bike for GPS navigation at times.
Lets get to it!
Decent budget
Used 81xx 88xx 83xx
When you have a budget of 6k to about 10k ish you can get some really good deals on the above mentioned phones. The 88 series is legendary and its really really light and has amazing battery life. Althought the OS is dated now because of arrival of 4.6 on the newer sets these phones are still very very capable and are hightly reccomended for people who want to test if a BlackBerry would fit their lives. The 88 series is also great for people who work in green areas where cellphones with camera's are prohibited. The Curve is a legendary phone and I will hightly reccomend it. And the Pearl I dont like so much because of absence of a full qwerty although it can do everything here that the others can. Any of the phones listed above are a very very good choice and you can find killer deals on them as well.
Decent Budget
New 88xx 83xx 8820
If you have a budget exceeding 10k ~ 20k you should go in for a brand new curve of if you want something extremely small and light the new pearl flip is also a good deal as it carries the new BlackBerry OS and also has WiFi. Functionality wise its all the same here. This is the budget most of the people would be looking at. I would highly reccomend grey market phones because they are considerably lesser priced.
Overkill
8900 Javelin, 9000 BOLD, 9530 Storm
Only buy these if you know what you want, although people which such high budgets know what they want but if you really are not familier with BlackBerries I suggest you play around with some second hand offerings first before ploughing so much cash into a cellphone.
Breakup of what I think of the phone in a single line (or little more

)
7100t - Lovely, Lloyd of Entrouge has one. Hate the SureType can be had for peanuts.
72xx - More of a collecters item today. Not of any real use other then a backup phone PERIOD.
87xx - Rugged, still can be used on BIS to a ceriein extent but you will find yourself upgrading before you can say "BLACKBERRY" amazing as a backup phone when you need BIS active on the backup set as well.
81xx (Pearl) - Amazingly light, can do everything that the curve can. Just a personal preference about the SureType keyboard. (I am scared of you Shaju)
83xx (Curve) - Amazing lovely fantistic, best bet as your first berry.
88xx - A great berry by all means if you dont need a camera. 8830 had some ringer issues and dont buy a 8830 for abroad thinking you can make it work on tata/reliance's CDMA network. It can be had very cheap!!
8220 (Pearl Flip) - Unimaginably small and light. Has the latest OS and is priced really well. Also has WiFi. It can fit in the Jeans Zippo pocket (lighter pocket)
8900 (Curve *codename* Javelin) - The new Curve, it ticks all the right boxes and is a worthy predessor to the old Curve. And is amazingly light when compared to the flagship BOLD.
95xx (STORM) - The Touchscreen Berry is great if you are not a heavy duty user (typing) it can do everything, the screen is gorgeous *fantastic* its extremely fundoo worthy gadget. Gotta upgrade the OS as soon as you get it though.
9000 (BOLD) - The Big Pappa of Berries, it commands a 10k premium over the 8900 although it doesnt really do anything that the curve cant (3G is a exception as its not here yet DUH!) Cant give you any real reason except you will love it and SNOB value.
Woah that was a big one. Any comments and help if needed I am here. I am most proally going for the Bold again its certein, there are a few new berries in the pipeline which people in the know would be aware of.