You will find the 2400 is very reliable system. I have installed many in networks using ACD and wireless and have no real major issues. I have worked on many that have been running for 5+ years with out an outage.

NEC has released new ACD platforms and new wireless is also available. If the system you have is older I would upgrade it to IPX so you can start to play with the IP Soft phones and IP trunks.
There are other trade in programs going on for phones and cards

Using the MAT commands makes programming easy , I seldom use Matworx to program a system.

Downfalls
NEC has a change in upper management, not sure if it is a good thing or not. I hope they continue with new upgrades and product roll out.
NEC does not market very well so you ll hear more about Nortel etc where you may have to seek out your NEC vendor to help with new product updates.
NEC does have a low part of the market so it does not always work on different 3rd party software , vendors do not want to spend time on developing software for a product that is not the hottest seller. Some systems like Nortel are easier to write software for.


Like any PBX you are going to work on it would be worth the money to get some training , it will make your life easier in the long run.