First of all, I did not face any of the "sarkari attitude" from MTNL. Registering, paying up, installation and commissioning happened in 15 days flat. I know atleast 5 other people from various localities who have had a similar or better installation experience.
Reliability has been top class, it can easily stand up to the carrier grade SLAs which corporates sign up for. The only downtime that I ever faced during the last three years was when some people stole underground cables, that too for not more than 3 cumulative days.
The support services, which may not be as polished as many of the private operators provide, are actually effective. Service is personalised, and much more forthcoming if you are not overly formal(the likes of "kya main aapa phone hold par rakh sakta hun" are thankfully done away with).
The throughput has been consistent as per the plan and billing plans are amongst the most competitive ones.
Nowadays they also provide anti-virus, anti-spamware service on a monthly basis.
I would easily give them 9 on 10, absolutely recommended.