What i understood from fiddling with my D60 for a month was how insufficient the on-board flash of the camera is. More than outright power its the 'directionability' of the light output that is restricted when it comes to on board flash.
So the hunt started for a Speedlite. There were two options the Nikon SB series and 3rd party flash units. Nikon right now has three speedlites, the SB400,SB600 and the pro SB900. Cost would range from 5K to 25K for the Nikon units.
The alternative is 3rd party flash units and there are dime a dozen! The main difference would be auto flash metering technology(i-TTL in Nikon speak).The Nikons are costly for a reason ie, CLS!(Creative Lighting system) and there are no brands that provide these on individual units(not considering the triggers).
I finally narrowed my options between the Nissin Di622 and the Nikon SB600. Nissin is also an old Japanese company and are relatively well known for teir Speedlite units.
Nikon SB600 Specs
Guide Number30/98 (ISO 100, m/ft), 42/138 (ISO 200, m/ft) (at 35mm zoom-head position, 20 C/68 F)
Electronic ConstructionAutomatic Insulated Gate Bipolar Transistor (IGBT) and series circuitry
Flash Exposure Controli-TTL, D-TTL, TTL (film based), Balanced Fill-Flash, Manual
Lens CoverageAuto 24 to 85mm, Manual 14mm to 85mm (14mm provided with built-in wide-flash adapter set)
Minimum Recycling TimeApprox. 3.5 seconds (manual, w/R6 (AA), 4.0 seconds (Lithium Ion AA), 2.9 seconds (NiCd AA), 2.5 seconds (Ni-MH AA)
Required Power Source4 x AA-type: Alkaline, Lithium, Nickel, NiCd, Ni-MH (All four batteries must be the same type)
Dimensions(W x H x D): Approx. 2.7 x 4.9 x 3.5 in. (68 x 123.5 x 90mm)
Weight10.6 oz. (300g)
Minimum Number of FlashesApprox. 200 (Alkaline batteries)
Wireless Flash Modes
Off
Remote
Wireless Communication ChannelsFour: 1, 2, 3 and 4
Channels
Wireless GroupsThree: A, B and C
Supplied Accessories
Speedlight stand (AS-19)
Soft case (SS-600)
Nissin Di622 Specs
Usable camera CANON digital camera, NIKON digital camera
Guide Number 44m, 145ft. (ISO 100), 62m, 205ft. (ISO 200)
Variable power 6 levels : Full - 1/2 - 1/4 - 1/8 - 1/16 - 1/32 powers
Flash exposure control E-TTL and E-TTL II for Canon cameras
i-TTL for Nikon cameras
Power source 4X LR6 or equivalent Mi-MH, lithium, oxyride batteries
Recycling time 0.2 -4.7 sec., with fresh alkaline batteries
0.2 -4 sec., with Ni-MH batteries
Energy saving system 5 minutes to stand-by mode, 30 minutes to shut down
Number of flashes 200-1500 flashes by fresh alkaline batteries
Illumination angle Digital lens : 16mm (14mm with wide angle diffuser)
by zooming reflector to - 18 - 24 - 35 - 47 - 57 - 70mm
Turning head 90upward, 90to left, 180 to right
Slave mode Slave sync : with respect to the digital pre-flash system
AF Assist light Infrared LED for distance of 0.7 to 6 meter.
Color temperature 5,600K (same as daylight)
Flash duration 1/800sec. to 1/20,000sec.
Accessories included Shoe stand, pouch
Dimensions 77(W) x 130(D) x103(H) mm / 30(W) x 51(D) x 40(H) inches
Weight 315g (without battery) / 11oz
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Did a hands on comparison between the two, the Nikon unit definitely feels better made but the Nissin is not far behind.The SB600 has an LCD and has a full CLS function set.The Nissin has LED display works in full i-TTL but works only as an optical slave.
Costs
Nikon SB600-Rs.11,500/-(Without B/W)
Nissin Di622-Rs.7,000/-(without B/W)
The budget at hand made the decision easy!

What drew in favor of the Nissin is that its more powerful than the SB600 , has a longer zoom range(upto 105mm against the 85mm of the SB600)-which complemented my 18-105 lens and also that the Nissin sported a fill flash card which the Nikon unit was lacking.

The flash lives for about 350 shots in -TTL mode and i am much impressed by the flash. About in door photos-well dramatic is an understatement! A hot shoe flash is an essential accessory for any D-SLR user.
The results
With On-board flash
With the NIssin Di622 on hotshoe(flash head with fill card bounced to the ceiling)
Both images were shot in a room lighted with a 15W incandescent light(quite faint).
The Nissin is available for both Nikon and Canon mounts and i guess are very good VFM alternative for single flash photography.