I LOVE themes, but, I also love to tweak their styles so that your site will look unique. While less sophisticated, I think you can get the idea on how different two sites built on the same theme can be:
If you tweak the design substantially, you will find that it may be more ecomonical to do a custom one. Most of our clients use a theme for a base and have us tweak the design by changing the color pallet, fonts, backgrounds or borders.
Some things to consider when choosing a theme:
1) The themes save you the most time on your layouts. Ignore the styling when viewing a theme and think of the layouts because those take the most time to customize.
2) Think about content… i.e., do you need to have the inventory status of a product show on the product in grid view? Does it have important additions like banners over images displaying attribute-based or category-based information like “exclusive product” or “clearance item.” Those can be hard to replicate.
3) Make sure you are happy with the layouts on the product detail pages. The other pages are easier to customized.
4) Make sure the theme has a satisfactory checkout process. For example, if you like a one-page checkout, but the them uses multi-page, it will probably take more work to customize your checkout process, or integrate a one-page checkout module into your theme than to customize a theme that has the desired functionality.
4) Any CSS component (fonts, colors, borders, etc.) are easily modified. Don’t discard a theme if you don’t like them.
5) Some themes come with modules, i.e., additional control panels for slide shows, etc. Those can be handy if you aren’t comfortable changing file names, path to images and the like.
6) Some themes have a price for you to be the exclusive user. If exclusivity is important to you, it is often worth taking it off the market for others.
7) Themes that have very rich content (multiple sliders on a page, sliders with many images, etc.) may take a long time to load. Look for comments with regards to load time or other hidden issues if the theme is sold on the Magento Connect store. If it is not, you might want to ask yourself, “why not?”
8) Make sure the company you are purchasing the theme from is reputable and has been around for a while. Google the company before buying anything from them to make sure there are no red flags about their reputation.
If you need some advice on choosing a theme or want some help in the vetting process, please visit our merchant services shop