NT8 is in alpha and will be in beta sometime this year... for an actual GA (General Availability) release... if NT7 is any indication you are talking years out.
You will need to define what "professional" means to you...
You will not find at any institutional desk (buy/sell side) NinjaTrader... you will find the likes of Bloomberg, Reuters, Redi, XTrader, CQG, etc... and you will also find a lot of custom OMS/OE systems (basically in house created tools for risk mgmt, pre-trade clearing, position offsetting, etc.) ...
but if by "professional" you mean any "prop" (and I use that term completely loosely) then you will find a variety of tools depending on the product being traded and the market connectivity they will have... so you might find sterling, lightspeed, CQG, XTrader, CTS, Vantage, etc... and you might even find NT7/MC/IRT...
and all "new comers" tend to use NT7 because it is free for simm and they believe that trading in simm is an indication of how they will do in real life, but the fills are never realistic and the pressure of actual money never exists on simm.
IMO, The most realistic simm I know off that we have access to as retail (for futures at least) is on XTrader... the second best, on CQG... and the most realistic from a inst desk side I forget the name now, but it was fun to use it... I had to take a "trading class" which has you behaving as the trader and you had to make markets on your issues and be flat at end of the day... you will get calls from buy/sell side and you had to always take the counter, offset in the market, and track what your book had and be as close to flat as possible at the end of the day or offset with futures... sometimes you will have profit because you stayed ahead of the desks calling you and you were quick to offset, others a loss... that was a fun simulator...
now, my advice... pick the platform you will use based on what you will be trading and what features you are looking to benefit from by trading the products you will focus on...
I use CQG because of the spreader, I could have used XTrader as well... but I like CQG a bit better because I got used to it... that is my main trading platform (even for "automated")... it also has backtesting which I quickly use to prototype ideas (not that I am that good at it)
I own licenses for NT7 and Multicharts and MultiCharts.NET, as well as Amibroker, two of each... I use them sometimes for backtesting and for some automated trading that I want to do but havent done yet...
Amibroker is best for basket trading and the type of trading I want to focus on long term... MC is best for the active trading, just not baskets... I dont completely trust their back testing, as I prefer to always forward test anything...
anyhow, just my 2 cents given I had some time right now..