I personally use Log Me In and I have both Rescue and Central.
Central is fantastic for business clients, as I can install the app on servers and workstations which allows me to quickly and easily remote into them. It also has alert packages that will tell you a multitude of things (high mem usage, disk space, etc etc), but my favorite is the event alert. I set this up servers so it emails me if any error or critical events get logged.
A couple months back I had an email about a server going offline on a Friday night. Sat morning I went to check on the server to discover it had crashed, and I was able to get it back online before everyone got to work on Monday - thus avoiding the frantic Monday "HEEELLLLPPP" call that I would have to somehow jam into my packed schedule. Total life saver, both for me and my client!
Central can also automatically run scripts... defrag, definition updates, scans, etc... a new feature they just added is automatic updates, which is quite nice.
Rescue is also quite amazing for regular remote support. I have the branded app integrated into my website, and it's very easy to get connected. Once connected I can remotely manage the computer (obviously), swap files back and forth and even install the desktop remote app that they can run instead of visiting my website every time. You can reboot, reboot into safe mode, log on and off of computers without losing connection...
So, tons of awesome features... The downside is the price. Rescue is about 1200/yr right now I think, and Central is an additional fee. That's not so bad, I can deal with that - by cost problem run with the client licenses. Free ones work for simply having an easy method of remoting into a PC/Server, but in order to have the automation, alerts, swap files and all the other toys it cost 40-50/yr for each computer license (a Pro license). For a business to have that on the server is no big deal, for a business to have one on each workstation it still not horrible but is a bit hefty. However, because I primarily do residential support, it's a lot for a user with 3-4 computers in the house... especially when they have to pay for my time on top of it. I'm still trying to figure out how I can offer a high level of automation and support features like i mentioned above to residences.
So, there's my experience with LMI... If anyone else knows of a cheaper alternative that does everything that LMI does I'm sure the OP would love to know about it, I know I certainly would!