I have used IRCTC many times for booking tickets and my experience with them is awesome. I do agree that the website becomes slow while tatkal ticket booking but that is due to heave load on the server and we can not blame IRCTC for this. Recently they have changed their system and now per minute 7000 tickets can be booked whereas earlier it was only 2200 tickets per minute. Other corrective measure are no agent booking allowed and different time for AC and NON AC Passenger and all this happy changes have drastically changed everything.
I can now book or cancel ticket easily which is very nice thing. Money refund are quick. The website is ad free and fast to load, however I feel that they should delete the CAPTCHA option or at least make them real easy. Rest all is fine.