Yeah, Sketchup is really poor with high poly so when details start to rise or you start cramming loads of stuff in, its time to start using layers effectively and if you can, find the tutorials on external linking or using proxy objects to keep scenes manageable.
I love Sketchup though as an easy modelling package, so it suits me and my needs perfectly though. Combined with Indigo its been hugely influential in how I work. Its great for simple geometry and with a big of jiggery pokery you can produce some really good images - just look at one of the users on here Pibuz work, he's a Sketchup user and the results he gets from the software are stunning.
For example here by Pibuz, http://www.indigorenderer.com/forum/vie ... 14&t=11834
just look at that glorious texturing work, lighting, scene dressing etc - and its all done in sketchup.
So I wouldn't say you have to go for 3DSMax straight off to get spectacular results. A lot of the power users on here use Blender which is free. I've tried it and my brain exploded as it seems to ignore every single convention for user interfaces I'm familiar with (even a saving a file seemed to be idiotically complex) so I never got anywhere, but the results on here prove its clearly possible to do some stunning work if you're cleverer than me!
Its worth considering what you want to achieve with a render when you start, and crucially, what you can actually
achieve. I've done a number of visuals for clients who own UK industrial parks (really exciting stuff I know) where its simply not possible to put in the amount of detail that the actual site contains and it becomes impossible in the time constraints to put in everything surrounding the site that should logically be there - signage, buildings, street furniture etc etc (its also not always preferable, the images I produce are meant to sell and idea for marketing purposes etc, so filling them with the crap that clutters the actual world only detracts from the intention) - which then hurts realism slightly meaning no matter how carefully I texture things up or light scenes something will always seems a little....off. The brain sees a road and thinks "huh, that road is a bit too smooth, wheres the drain covers, wheres the cracks"
and so on.
Which is normal, but when you a) don't have to time to model a road beautifully realistically, and b) don't want to as its not intended to draw focus from the actual focal point of the scene, ie its just 'set dressing'; my solution is not to go for super realism which I just won't achieve with the tools, skills and time available, the solution is to stylise the scene and mix the rendering capabilities of Indigo with a more artistic slant as to what looks good, blending Indigo renders with line output from Sketchup styles, blur effects, paint effects etc all intended to give an impression of the proposals without going to the nth degree as I don't have the time (or the skills) available.
And it works, these images are well received by clients and because they're not purporting to be uber realism, the clients don't spy the omissions or exclusions. It doesn't matter that there are no speed limit signs, rubbish bins, realistically cracked pavements etc - they see the image as a whole and accept it for what it is. Stylising things often means the brain discounts things it would normally flag up as Not Quite Right.
My point is, set your sights to the achievable. If you have no time limit, by all means spend weeks on a project, crafting and modelling and making it like a photograph. If not then there are lots of little tips and tricks you can use to give the impression
of realism without going mental.