I started using Pentax gear in about 1973 or so. I've been tempted to switch brands at various times over the years, but after careful consideration, the costs always outweighed the rewards for me. Those debates with myself generally go something like this: Right before opening this thread, I was reading the thread where one of our members had adapted a Leica 180mm lens to Pentax K mount. I've always admired Leica's stuff and I was thinking to myself, "Man, that would rock! I'd love to have a Leica lens in K mount!" But then I asked myself, "Okay...you already have a Pentax A* 200mm f2.8. Considering the cost of finding a 180mm Elmarit and converting it, are your picture taking capabilities going to be improved more than say...oh...taking the money you'd spend on the Elmarit, applying it towards a 50-135 f2.8 and keeping the A*200mm?" Hmmmm....no, probably not......dang it.