Although I purchased my large format equipment specifically for commercial work, and I use it almost exclusively for commercial work, I have to say that I was surprised that it quickly became my favorite equipment for play with on landscape and architechural photos too! If you are a serious amatuer photographer, you should consider adding large format equipment to your list of toys!
I have a modest collection of Large Format equipment. Although my Nikon F100's F8008 & F801 cameras are my stock day-to-day equipment. I must say I enjoy my Large Format equipment the best.
Yes the 35mm auto everything (with manual overrides used frequently) is very convenient and easy to carry, and yes you can shoot faster with 35mm. And point and shoot "carry them in your breast pocket" cameras are great on vacation. But Large format is beautiful and artistic and flexible beyond belief. So why do I still shoot 99% 35mm?
My camera of choice is an Omega View 45e (4x5) camera. That means the film is many times larger than my 35mm equipment. - 4"x5". I was amazed the first time I saw a 4"x5" "slide." Beautiful.
I have an excellent Schneider 210 lens (For 35mm buffs, that roughly equivalent to a 120mm lens.) This lens is my most common used lens. It is crystal sharp, right to the edges, has lots of coverage for the special shots that can only be done with large format equipment. The light does not fall off until the very last 1/4" of it's coverage, and even that's not bad (And with large format, you don't necessarily use that last 1/4" unless you are really pushing the limits of the equipment).
I have a good Raptor 90mm lens (Wide angle lens) It is quite sharp to the edges. Has acceptable coverage for shots like tall buildings. (With wide format equipment you can shoot a tall building from the ground and it looks like you shot it straight on - not falling over like 35mm and medium format equipment typically does.)
My heavy duty Manfrotto 161 tripod is fantastic. I admit, it's 30lbs can be a problem at times, but it is rock solid and holds the heavy equipment easily. It is paired with a Manfrotto 029 head with 3 separate controls in the 3 axis. Much better than trying to level off with even a great ball head.
Of course I have a variety of misc. options, an 8x loupe, a black sweater used as a hood, remote releases, polaroid back, but my most indispensable option is my Minolta IVF meter. This is a spot/ambient/flash meter. It lets me read the light at a spot (typically I reflect off my 18% grey card for this,) or place the meter at the subject to read the light falling on the subject, or, with a flash, read the reflected light from the flash.
Finally, I have color cards and gray scale cards for taking pictures of paintings and other reproductions where it is critical to reproduce as close to the exact colors as possible all the way from film, prints, computer images, magazine covers.
Personally, I think every serious amatuer and most professions should have a large format camera in their equipment list - just don't get rid of your normal day to day cameras.