Tamron makes quite decent glass, and some quite knowledgeable people say their vibration control is as good or better than the big boys' versions. Lens creep can be a bother, if the camera is oriented vertically, but that is true of all superzoom SLR lenses, including Nikkor and Canon. My wife and I have personal experience with pre-VC Tamron 18-200mm lenses on Nikon and Canon cameras. She likes the superzoom concept; I do not. She accepts lens creep and sharpness compromises at each end of the focal range in exchange for not ever having to swap lenses in the field.
True, there is a latch to prevent creep, but it only latches at the 18mm setting.
If you have a Canon, be SURE to buy the right version! Di is for full-frame Canons, Di II is for cropped-frame Canons. Di will fit cropped-frame Canons, but the electronics will not "talk" to each other.
Superzooms are not without merit! My wife can get a shot at a distant bird or something, while I miss some opportunities due to having the wrong lens mounted. On the other hand, I am more likely to have my camera in hand, with a fixed-focal-length 50mm making the whole package handier.
Just to be clear, my wife is much more experienced and talented than I am.
Canon 7D2/7D/5D/40D/1D2N/M3; Nikon F6/D700/FM3A/1Dx/Coolpix A; Canon 40mm 2.8 STM, 135L, 50L, 35L, 50mm 1.8 I, 100mm 2.8L Macro, 10-22mm EF-S, 400mm 5.6L, 16-35mm 2.8L II; Nikkor 50mm 1.2 AI-S, 50mm 1.4G, 50mm 1.8D, 16mm 2.8D Fisheye, 180mm 2.8D, 100-300mm 5.6 AI-S, 45mm 2.8 AI-P, 14-24mm 2.8G, 24-70mm 2.8G, Micro-Nikkor 60/2.8G; Voigtlander 90mm f/3.5 SL II, Zeiss ZF.2 2/135 APO