It is all up to you.
I'm sure you estimated your website traffic. If your website has a lot of visitors in and out very often, you may need DH PS.
In the meanwhile, you can always check your website uptime, if the uptime is unstable or too bad, you are in a bad server (no luck). You may either send alarm to DH Admin or consider to have DH PS.
Save $97 (MAX Discount) with code: [color=#CC0000]97YES[/color] [url=http://dreamhost.com/r.cgi?296804/signup|97YES]Sign Up NOW[/url] or More Codes here