Ok so I have used the following broadband providers
Sify ( Cable )
Exattnet ( Cable )
Reliance ( WiMax )
BSNL ( ADSL )
Airtel. ( ADSL )
I have been a subscriber of each ISP for upwards of 6 months and some even beyone 1 year .
In my experience with the above mentioned ISPs Airtel has given me between 95 to 99% uptime [ that's what really matters ] and the speed has always been more than promised in short, Airtel as an ISP has always been over and above my expectations , Finally , FINALLY !!! , I have found an ISP that I am going to stick with .
1st Rule of thumb
When looking for an ISP , consider the following in the order mentioned below
1) Uptime
2) Customer Service / Tech Support
3) Price
2nd Rule of thumb
1) Never ever ever go for a limited plan , what's the point of having a pack where you get 2 Mbps but have a 2 / 4 GB bandwidth cap , you are bound to download more with the high speeds i.e. stick to unlimited plans .
2) When ISPs refer to Download limit this includes total data traffic to your machine , [ downloads + uploads + surfing + watching videos on youtube etc etc ] I have seen many people shocked when they get bills of Rs20,000 saying that I didnt download anything , I only used to watch movies online !!!

, again I cant stress more on the fact that unlimited plans are the way to go !!!
Well then again if your requirement is high uptime and good download speed , Airtel Zindabaad , look at the poles you will understand .
