I have the M12 also, has been working great for about 4 years now. If you need a reason to get into the M12 battery system, this is a great reason, and you will have one of the largest selection of other tools to run from the M12 system. You could go M18 also, but it is about $100 more. If you already have 18v LXT, M12 might be a better choice as a compact alternative to your LXT.
Some choices, for $179 you can get this with 1 XC battery
http://www.amazon.com/dp/B00396JTKO/?tag=atomicindus08-20
For a different investment (more money), you can find many places that have the bare tool + FREE XC battery for $129, here's an example
http://www.acmetools.com/shop/tools/milwaukee-2446-20-m12-lithium-ion-grease-gun
And at home depot they have they awesome deal for $129
http://www.homedepot.com/p/Milwauke...XC-Battery-Pack-2494-22B/205482513?quantity=1
For $258 (2 x $129) you would have 1 charger, 4 batteries (2 XC 2 regular), 1 grease gun, 1 drill, 1 impact driver and 2 cases. The HD deal is not the Fuel line but still excellent.
Also, not sure where you are located, something offered by Makita in Canada (Australia & NZ also) is
http://www.makita.ca/index2.php?event=newaccessorydetailstemp&id=514&from=tool
Not exactly an LXT tool, this would probably work on any drill, and for $100 I would spring the extra for the M12.
No experience with the Lincoln, most other threads I have read, people that had it were satisfied. This thread is the first I see more than one person being not too happy with the batteries.
Definitely other battery guns out there, good luck!