Right now i have 12 18V Ryobi batteries si my main reasoning to not buy the gun is it'd mean having to get another set of batteries, which is the main reason I've stuck to the 18V Ryobi stuff for compatiability reasons since I used to have 3 different makes of tools/bateries/chargers, it gets to be a PITA to say the least which I'm sure many of us here can relate too.
When I get a run of replacement windows I use the heck outta my caulk gun for laying inital bead on the outside stop before I set the window in the opening, other than that I dont use it nearly as much as somebody in the painting profession would-I could totally justify one for that feild of work...smoother bead=less time perfecting it. And for the welding comment, can also see that as a 2 sided coin, for those of us that take the caulk to the extreme perfection

it'll just make it that much better/easier for professional results...but for the all to common silicon freak, it would spell certain disaster and even more caulk/silicone on everything else but what they intended to use it for.
Funny story: We were part of a group that was hired to replace 325 windows in an apartment complex and there were 2 teams, my team of guys-4, and the other team of guys we knew of but never worked with consisting of 5 guys. Long story short, at the end of the job, the general called the other crew in and asked how it was they-and I'm NOT exagerating-used a case of silicone PER WINDOW!!!! Retail cost on case of the stuff we were using was $121+tax/per case. Once he went to the job sight and seen the windows our crew did and then the windows the other crew did with the silicone fetish, it was easily apparent. We stuffed the windows with fiberglass batt for insulation and capped the outside blind stops with aluminum....the other crew was silicone for everything-even used the silicone as "paint" and slathered it all over the outside work stops to make them white

The windows were all mortored into the limstone facade and were tough getting the first few out until we figured oout the easy way- air chiesel and sawzall, the other crew ways....take crow bars and literally bust the glass....INTO THE APARTMENTS with no tarps or anything to catch debris, then start bending the steel frames into submission until they were contorted enough to jerk out of the opening, often ripping out large chunks of mortor and peeling the paint from interior walls where the drywall butted upto the windows.
All the times I second guess myself in this insdustry asking myself "I'm good enough" to be compared to other contractors I either think back to past jobs I've seen/been on with those kinds of idiots and it's all the reassurance I need.