Approach Shoes: 5.10 Guides
Well, they are fall within the category of Approach Shoes in the 5.10 catalogue, but the Guide Tennie could easily sneak into the chunky rock boot pages. The original Tennies appeared many, many years ago, and have been so succesful that they not only linger on, but have been modified and are now better than ever.
The most crucial thing to get right when buying a pair is the size. You want them small. It's no use having your feet sliding around and your toes banging against the protective toe box, these shoes are designed for climbing in, so get a snug fit. That said, get them too small and you'll overheat as soon as you start walking in them (spoken from previous experience!). If you plan to climb in them you don't want to be able to put your finger down the back between the shoe and your heel (as shop shoe fitters will tell you).
The first thing that you will notice about them is the mass of rubber. Unlike standard approach shoes, which often appear more like running trainers, the rubber is everywhere! On the sole is the trademark Tennie 'Stealth C4 (same as the climbing boots) Dotty' rubber. When smearing the lack of moulded shaping in the sole provides, I would confidently say, more grip than any climbing shoe I have ever worn. This is due to the proven stickiness of Stealth C4, combined with the larger surface area than in any equivalently sized rock shoe. Although there is a slight 'rocker' built into the last to ease walking, the curve is far less pronounced than a regular approach shoe, and more similar to a performance rock shoe, allowing a whole lot more stability when climbing. The Dotty rubber is replaced by a regular Stealth C4 rand, which overlaps the toes and heel well enough to make crack climbing a breeze. The only aspects of climbing that is not on a par with rock shoes is edging, and using any small foot-holds / pockets. Whilst the edges are good (i.e. way better than a standard approach shoe or trainer), they are not a patch on rock shoes. That said, I was happily climbing E1's on Gritstone in them recently.
Other notable features include the fact that the bridge has been widened to make standing in etriers and slings more comfortable - a clear signal that these shoes are also designed for big walling. The green uppers have been 'tightened' up, the old diamond patches' replaced with a starlike stiching mosaic to give the shoes a really nice look, as well as increase in durability.
The catalogue stated that they are comfortable and supportive for long approaches, and technical enough for thousands of feet of difficult climbing. On a recent trip to Wadi Rum in Jordan I put this claim to the test. Over A two day route up and down Jebel Rum I was comfortable (in the direct sun), and confident for the entire time.
Another anecdote worth recounting, and one as different from desert sandstone climbing as possible, is the time when Nick Dixon reportedly strapped a pair of crampons to his Tennies (not recomended by the manufacturer blah blah) and solo'd a bunch of ice routes in North Wales.
I really don't see how you could better these as a compromise lying somewhere between rock and approach shoes, and overlapping snugly into both markets.