Pls note that mtnl's plans are diff from airtel's... The mtnl plan gives 1mbps during day & 2mbps at night without any FUP... While airtel gives 4mbps speed till 30 gb than 256kbps after that... In my humble opinion mtnl's plan kicks airtel's plans butt zzz... Anyway to solve ur buffering prob u could go for mtnl's 888/month plan which will give u 2 Mbps at night & is in the sub Rs 900 range...
Oh, I know. Actually, I am on MTNL's new plan right now: DSL_COMBO_1249 which gives speeds upto 2 MBPS (day & night both) but has a FUP of 20 GB (upload+download) which is fine for me because my usage from July 1-July 31 was only ~12 GB totally. So, basically for me, FUP isn't the problem because I'm not a heavy downloader. My main concern is speed.
If Airtel is giving me 4 MBPS by just paying an additional Rs. 150/- with 30 GB FUP that too, I would definitely like to try it out atleast. But I'm only concerned about the quality of Airtel broadband connections in Mumbai and if there are no additional costs/glitches involved with Airtel.