I have not set up a SEPP through TD Ameritrade but my wife has a TIRA with them and I manage the account.  My experience with TDA has been reasonably good.  They do a good job with the simpler aspects of investing. I have done quite a bit of buying and selling of mutual funds and stocks. Their service has been good in this area.  The info on their web site regarding SEPP plans is virtually nil, however, and it would be necessary to call them to see what they can do in this area of investing / planning, if anything.

My SEPP was set up with Vanguard and that worked reasonable well.  They do not take any interest in a client's SEPP, however, and it is necessary to file a form 5329 to claim the 72t exception to the 10% early withdrawal penalty tax.  Vanguard treats client SEPPs the same way as they do any periodic IRA withdrawal. While this is not particularly helpful, it is also not especially unusual among custodians these days.

That said, a number of people have commented on this web site that they have had very good experiences with Charles Schwab.  Apparently, Schwab shows an interest in their clients SEPP accounts to the point of assisting with the SEPP setup and reports a "2" in box 7 of the 1099-R.  At least, they used to do this.  Don't know for sure if they still do it or not.  I would check with Schwab about an IRA account with a SEPP plan. 

Ed